It is known to use, for example in some vessels of pressurized fluid and/or granular material in movement, shafts or bars on one or more levels, which pass through the whole vessel transversely and, with movements of partial or complete rotation, induce new conditions of physical equilibrium, for example to prevent possible discontinuity in the stream of granular material being processed by the vessels. Furthermore, the shafts allow to prevent the formation of agglomerates or bridges caused by the pressure, in the range of many tons, which the column of material above exerts on the lower part.
The support devices for the shafts, which can have a range of diameters comprised between about 400 mm and more than 1000 mm, are normally positioned in correspondence with the ends of the shafts, and are disposed outside the vessel.
In correspondence with the apertures made in the lateral wall of the vessels, and in order to allow the shafts to be inserted, it is also known to use sealing devices which isolate the inside of the vessel from the outside, and allow the shafts to rotate, at the same time preventing leakages of fluid, which can also be at high temperatures, for example comprised between about 800° C. and about 1000° C.
Sealing devices are known, made of a plurality of annular elements, normally 5 or 6, with a square cross section and consisting of synthetic fibers, wound with each other in a plait and compressed by a rigid element, such as for example a connection flange, in a toroid seating situated between the shaft and an interface flange, solid with the vessel, or connected with a flexible element acting on a vertical plane.
One disadvantage of these known devices is that they are not able to keep themselves coaxial with the shaft when the latter is in a non-centered position with respect to the vessel as a consequence of the dilatation of the lateral wall of the vessel caused by high inner temperatures. The displacement of the lateral wall causes an asymmetrical deformation of known sealing devices, which are excessively compressed in the lower part of the shaft, whereas in the upper part spaces can be created from which gas could leak from the vessel, in practice reducing the effectiveness of the sealing devices. In the light of these problems, the only possibility is to compress the seal and the consequent reduction in the duration thereof.
From EP-A1-1186811, EP-A1-0052423, U.S. Pat. No. 2,624,599 and EP-A1-0970743 sealing devices are known which are configured to seal an aperture in which a rotating shaft is inserted. These known sealing devices are able to compensate for axial displacements of the shaft or for one-direction radial movements, such as vertical displacements. All the above mentioned sealing devices are yet not configured to keep the aperture sealed in case of multi-direction shaft displacement, for example defined by an axial and two radial displacements, vertical and horizontal, or lateral, ones.
Purpose of the present invention is to obtain a sealing device which, in any operating condition, irrespective of the amount of the flexion to which the shaft on which it is mounted is subjected, and for every relative movement between the interface flange of the vessel and the shaft itself, guarantees the correct seal of the aperture of the vessel where the shaft is inserted, responding efficiently to the movements described above.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.